Carbohydrates are the fundamental building blocks of many natural polymers, their wide bioavailability, high chemical functionality, and stereochemical diversity make them attractive starting materials for the development of new synthetic polymers. In this work, one such carbohydrate,
Neodymium‐based catalysts coordinated with phosphate ligands (NdCl3·3L), where L = triethyl phosphate (TEP) or tris(2‐ethylhexyl) phosphate (TEHP), were synthesized. The ring‐opening polymerizations (ROP) of ɛ‐caprolactone (ɛ‐CL) with these catalysts in the presence of benzyl alcohol initiator were performed, yielding polymers with well‐defined molecular weights and relatively narrow polydispersity index (PDI = 1.22–1.65).
- PAR ID:
- 10067038
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Polymer Science Part A: Polymer Chemistry
- Volume:
- 56
- Issue:
- 12
- ISSN:
- 0887-624X
- Page Range / eLocation ID:
- p. 1289-1296
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
ABSTRACT d ‐glucopyranoside, was utilized to produce a hydrophobic five‐membered cyclic carbonate monomer to afford sugar‐based amphiphilic copolymers and block copolymers via organocatalyzed ring‐opening polymerizations with 4‐methylbenzyl alcohol and methoxy poly(ethylene glycol) as initiator and macroinitiator, respectively. To modulate the amphiphilicities of these polymers acidic benzylidene cleavage reactions were performed to deprotect the sugar repeat units and present hydrophilic hydroxyl side chain groups. Assembly of the polymers under aqueous conditions revealed interesting morphological differences, based on the polymer molar mass and repeat unit composition. The initial polymers, prior to the removal of the benzylidenes, underwent a morphological change from micelles to vesicles as the sugar block length was increased, causing a decrease in the hydrophilic–hydrophobic ratio. Deprotection of the sugar block increased the hydrophilicity and gave micellar morphologies. This tunable polymeric platform holds promise for the production of advanced materials for implementation in a diverse range of applications. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2019 ,57 , 432–440 -
more » « less
ABSTRACT Copper‐catalyzed azide‐alkyne cycloaddition polymerization (CuAACP) of AB2monomers demonstrated a chain‐growth mechanism without any external ligand because of the complexation of
in situ formed triazole groups with Cu catalysts. In this study, we explored the use of various ligands that affected the polymerization kinetics to tune the polymers’ molecular weights and the degree of branching (DB). Eight ligands were studied, including polyethylene glycol monomethyl ether (PEG350,M n= 350), tris(benzyltriazolylmethyl)amine (TBTA), 2,6‐bis(1‐undecyl‐1H‐benzo[d]imidazol‐2‐yl)pyridine (Py(DBim)2), 2,2′‐bipyridyl (bpy), 4,4′‐di‐n ‐nonyl‐2,2′‐bipyridine (dNbpy),N,N,N′,N″,N″ ‐pentamethyldiethylenetriamine (PMDETA),N,N,N′,N″,N″ ‐penta(n ‐butyl)diethylenetriamine (PBuDETA), andN,N,N′,N″,N″ ‐pentabenzyldiethylenetriamine (PBnDETA). All ligands except PEG350exhibited stronger coordination with Cu(I) than the polytriazole polymer, which freed the Cu catalyst from polymers and resulted in dominant step‐growth polymerization with simultaneous chain‐growth feature. Meanwhile, the use of PEG350ligand retained the confined Cu in the polymer, demonstrating a chain‐growth mechanism, but lower polymer molecular weights as compared with the no‐external‐ligand polymerization. Results indicated that aliphatic substituent groups on ligands had little effect on the molecular weights and DB of the polymers, but rigid aromatic substituent groups decreased both values. By varying the ligand species and amounts, hyperbranched polymers with DB value ranging from 0.53 ([TBTA]0/[Cu]0= 5) to 0.98 ([PMDETA]0/[Cu]0= 2) have been achieved. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2018 ,56 , 2238–2244 -
more » « less
Abstract Ring‐opening polymerization (ROP) of lactones or cyclic (di)esters is a powerful method to produce well‐defined, high‐molecular‐weight (bio)degradable aliphatic polyesters. While the ROP of lactones of various ring sizes has been extensively studied, the ROP of the simplest eight‐membered lactone, 7‐heptanolactone (7‐HL), has not been reported using metal‐based catalysts. Accordingly, this contribution reports the ROP of 7‐HL via metal‐catalyzed coordinative‐insertion polymerization to the corresponding high‐molecular‐weight polyester, poly(7‐hydroxyheptanoate) (P7HHp). The resulting P7HHp is a semi‐crystalline material, with a
T mof 68 °C, which is ~10 °C higher than poly(ε ‐caprolactone) derived from the seven‐membered lactone. Mechanical testing showed that P7HHp is a hard and tough plastic, with elongation at break >670%. P7HHp‐based polyesters with higherT mvalues have been achieved through stereoselective copolymerization of 7‐HL with an eight‐membered cyclic diester, racemic dimethyl diolide (rac ‐8DLMe), known to lead to highT mpoly(3‐hydroxyburtyrate) (P3HB). Notably, catalyst's strong kinetic preference for polymerizingrac ‐8DLMeover 7‐HL in the 1/1 comonomer mixture rendered the formation of di‐block copolymer P3HB‐b ‐P7HHp, showing two crystalline domains withT m1 ~ 65 °C andT m2 ~ 160 °C. Semi‐crystalline random copolymers withT mup to 164 °C have also been obtained by adjusting copolymerization conditions. Mechanical testing showed that P3HB‐b ‐P7HHp can synergistically combine the high modulus of isotactic P3HB with the high ductility of P7HHp. -
more » « less
ABSTRACT Charge transport in conjugated polymers may be governed not only by the static microstructure but also fluctuations of backbone segments. Using molecular dynamics simulations, we predict the role of side chains in the backbone dynamics for regiorandom poly(3‐alkylthiophene‐2,5‐diyl)s (P3ATs). We show that the backbone of poly(3‐dodecylthiophene‐2‐5‐diyl) (P3DDT) moves faster than that of poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) as a result of the faster motion of the longer side chains. To verify our predictions, we investigated the structures and dynamics of regiorandom P3ATs with neutron scattering and solid state NMR. Measurements of spin‐lattice relaxations (T1) using NMR support our prediction of faster motion for side chain atoms that are farther away from the backbone. Using small‐angle neutron scattering (SANS), we confirmed that regiorandom P3ATs are amorphous at about 300 K, although microphase separation between the side chains and backbones is apparent. Furthermore, quasi‐elastic neutron scattering (QENS) reveals that thiophene backbone motion is enhanced as the side chain length increases from hexyl to dodecyl. The faster motion of longer side chains leads to faster backbone dynamics, which in turn may affect charge transport for conjugated polymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.
2018 ,56 , 1193–1202 -
more » « less
Abstract Polymerization‐induced self‐assembly (PISA) has emerged as a scalable one‐pot technique to prepare block copolymer (BCP) nanoparticles. Recently, a PISA process, that results in poly(
l ‐lactide)‐b ‐poly(ethylene glycol) BCP nanoparticles coined ring‐opening polymerization (ROP)‐induced crystallization‐driven self‐assembly (ROPI‐CDSA), was developed. The resulting nanorods demonstrate a strong propensity for aggregation, resulting in the formation of 2D sheets and 3D networks. This article reports the synthesis of poly(N,N‐ dimethyl acrylamide)‐b ‐poly(l )‐lactide BCP nanoparticles by ROPI‐CDSA, utilizing a two‐step, one‐pot approach. A dual‐functionalized photoiniferter is first used for controlled radical polymerization of the acrylamido‐based monomer, and the resulting polymer serves as a macroinitiator for organocatalyzed ROP to form the solvophobic polyester block. The resulting nanorods are highly stable and display anisotropy at higher molecular weights (>12k Da) and concentrations (>20% solids) than the previous report. This development expands the chemical scope of ROPI‐CDSA BCPs and provides readily accessible nanorods made with biocompatible materials.
